Re:clock mechanism

I couldn't believe you finished the armors ! The left one, after you put exactly as the blueprint said, give you a mallet, hammer at the bottom.
The right one give you a handle (also at the bottom), then the doors opened!

Try uninstall and install the game again, if not solution it's a glitch (CS will help you!).

Re:clock mechanism

After you put the two armoured robots together, not only does the door open to the clock tower, but something opens on the bottom of each robot. One of the items is a sledgehammer, I think the other was a handle.